Regulation
2020 saw an unprecedented amount of regulatory intervention:
censorship around coronavirus, US elections, and racial issues

the offensive of the US authorities on Tik Tok

Apple's plans to restrict access to advertising identifiers and complicate user tracking rules for ad networks

here and there issues around personal data safety flare up
On the advertising front, there is already a ruling limiting so called misleads.
We’ll see more of this in 2021.

As for new formats, TikTok videos are becoming increasingly popular.